Why a kilogram of uranium beats a tonne of coal
Burning coal releases energy from chemical bonds between atoms — a few electronvolts per reaction. Nuclear fission releases energy from inside the atomic nucleus — about 200 million electronvolts per event. That's roughly a million times more concentrated, and it's why a fuel pellet the size of your fingertip holds the energy of a tonne of coal.
This calculator shows both the realistic and the theoretical picture. In a real reactor, natural uranium yields a few hundred thousand times its weight in fossil-fuel equivalent; if you could fully fission pure uranium-235, the figure climbs into the millions. Either way, the energy density is unlike anything chemical.
How the comparison works
The tool converts the uranium's energy release into kilowatt-hours, then divides by the energy density of each fossil fuel to find the mass needed to match it:
The CO₂ figure is the carbon dioxide that burning the equivalent coal would release — the emissions nuclear avoids. The homes-powered figure assumes typical annual household electricity use. To go further, size a real plant with the reactor output calculator, or explore the materials side with the radioactive decay calculator.
Frequently asked questions
How much coal does 1 kg of uranium replace?
In a typical reactor, around 14,000–20,000 kg of coal. Fully fissioned, 1 kg of U-235 equals roughly 2.7 million kg of coal — nuclear fuel is millions of times denser.
Why is nuclear fuel so energy-dense?
Fission releases energy from the atomic nucleus (~200 MeV per event), millions of times more than the chemical bonds released by burning fossil fuels (a few eV).
Does nuclear power produce CO₂?
Fission itself produces none. There are small lifecycle emissions from mining and construction, but generating from uranium avoids the large direct CO₂ of burning coal, oil or gas.